The dual role of ZnO nanoparticles for efficient capture of heavy metals and Acid blue 92 from water

ZnO nanoparticles were employed as efficient adsorbent for the removal of Cr3+, Co2+, and Ni2+ ions from aqueous solution. The metal uptake percentage of Cr3+ was higher than Co2+ and the Co2+ was greater than Ni2+. The obtained ZnO-Cr3+, ZnO-Co2+, and ZnO-Ni2+ nanoparticles have been characterized by FT-1R, XRD, EDX, SEM, and TEM techniques. The impregnated metal ions are homogeneously dispersed on the surface of ZnO without altering its morphology. These materials (ZnO-Cr3+, ZnO-Co2+, and ZnO-Ni2+) were tested as adsorbents for the removal of Acid blue 92 (AB92) from aqueous solution. It was found that ZnO-Cr3+ was the more efficient adsorbent for the dye. Under several reaction conditions, the removal efficiency increased with the increase in the adsorbent dose and the initial concentration of the dye. The adsorption process was retarded with increasing the pH and addition of NaC1 and a triple mixture of salts (NaCI, Na2SO4, CH3COONa). The activation and thermodynamic parameters characteristics of the dye removal were determined. The value of activation energy obtained (25.71 kJ mol(-1)) indicated physisorption process. The dye uptake followed pseudo -second order kinetics and obeyed the Langmuir adsorption isotherm. ZnO-Cr3+ proved efficient catalyst compared with ZnO-Co2+, ZnONi2+ and pure ZnO for the catalytic oxidative dissipation of AB92 with H2O2 or irradiation with UV light. (C) 2017 Published by Elsevier B.V.